1. Field of Invention
Aspects of the invention relate to a driving circuit for driving an electro-optical panel, such as a liquid crystal panel, a method for protecting the same, an electro-optical apparatus, such as a liquid crystal apparatus, including the electro-optical panel and the driving circuit, and an electronic apparatus, such as a liquid crystal projector, including the electro-optical apparatus.
2. Description of Related Art
This type of driving circuit can be incorporated into a substrate of an electro-optical panel so as to serve as an internal circuit for driving scanning lines and data lines by using externally supplied power, or is attached to the substrate so as to serve as an external IC circuit. Such a driving circuit may be deteriorated or destroyed for various reasons: temperature, humidity and mechanical impact during a mounting or assembling step in a process of manufacturing the driving circuit or an electro-optical apparatus including the same, at shipment or while being stored, and while the product is being used after shipment. In particular, a problem is destruction caused by a stress of electrostatic discharge, i.e., electrostatic destruction, which occurs while the electro-optical apparatus is being assembled or transported. While the driving circuit or the electro-optical apparatus is being assembled, static is generated around the circuit or apparatus. When the static is applied to wiring connected to the driving circuit, the driving circuit is deteriorated or destroyed. As a result, manufacturing yield reduces and breakdown of products after shipment occurs.
In order to prevent such deterioration and destruction of the driving circuit caused by static, a protective circuit can be provided for a signal path through which a signal is input/output in the driving circuit. See, for example, Japanese Examined Patent Application Publication No. 3-54475, Japanese Unexamined Patent Application Publication No. 11-231345, Japanese Unexamined Utility Model Registration Application Publication No. 64-3827, Japanese Unexamined Patent Application Publication No. 8-22024, and Japanese Unexamined Patent Application Publication No. 10-303431. More specifically, the protective circuit can be provided as an input protective circuit for an input terminal, to which various signals including clock signals, inversion clock signals, and start pulses are input from the outside of the driving circuit. Alternatively, the protective circuit can be provided as an output protective circuit for an output terminal, through which various signals including scanning signals and end pulses are output to the outside of the driving circuit.
Since the above-described driving circuit is driven by a power-supply voltage, the driving circuit can be provided with a power line serving as a power-supplying path for supplying the power-supply voltage, as well as the above-described signal path. On the other hand, the above-described protective circuit is provided for the input/output terminals for various signals including clock signals, but the protective circuit is not provided for the power-supplying path. Therefore, in this driving circuit, the resistance of an internal circuit to static, which may be applied to the power-supplying path while the electro-optical apparatus is being assembled or transported, is weak. As a result, the driving circuit may be deteriorated or destructed by static applied to the power-supplying path.
Particularly, if the wiring capacitance in the power line is large, this problem may not become evident. However, as a pixel pitch becomes smaller or as a driving frequency becomes higher under a recent requirement for improvement in image quality, the above-described problem will become increasingly serious due to a decrease in the wiring capacitance of the power line.